Recently, materials of silicon carbide (SiC), gallium nitride (GaN), and the like, are used to improve the characteristics of the semiconductor devices. These materials have hardness higher than silicon and are more difficult to process than silicon. To flatten such as the hard materials, a planarization technique such as a CMP (Chemical Mechanical Polishing) method, and the like, has been used. However, the conventional planarization techniques have problems such as an insufficient polishing rate, degradation in the in-plane uniformity of the materials after polishing, and increase crystal defects in the materials